Step-by-step switch



T. W. TUTTLE ETAL March 12, 1963 STEP-BY-STEP SWITCH Original FiledMarch 19, 1956 3 Sheets-Sheet 1 -INVEINTORS THOMAS M TUTTLE March 12,1963 "r. w. TUTTLE ETAL 3,081,416

STEP-BY-STEP SWITCH Original Filed March 19, 1956 3 Sheets-Sheet 2 mayMarch 12, 1963 T. w. TUTTLE ETAL 3,081,416

STEP-BY-STEP swnca Original Filed March 19, 1956 s Sheets-Sheet awiry/777% l N V ENTO R S United States Patent 3,081,416 STEP-BY-STEPSWITCH Thomas W. Tuttle, Nutley, and George F. McCarthy, Teaneck, N.J.,assignors to International Telephone and Telegraph Corporation, Nutiey,N.J., a corporation of Maryland Continuation of application Ser. No.572,468, Mar. 19, 1956. This application Apr. 19, 1961, Ser. No. 104,1238 Claims. (Cl. 317-112) This invention relates to step-by-step switchesused in automatic telephony and more particularly to a switch contactbank construction employing printed circuitry and is a continuation ofapplication Serial Number 572,468 filed March 19, 1956, and nowabandoned.

One of the objects of this invention is to provide a printed multiplefor each level of the switch wherein a shield is provided between themultiples of adjacent levels.

Another object of this invention is to provide means to make thedistance between adjacent pairs of conductors as large as practical withrespect to the distance between the two conductors forming the pair inorder to minimize, without resort to transposition schemes, theelectrostatic and electromagnetic interaction between pairs ofconductors in a line bank level and between pairs of. conductors inadjacent levels.

Another object is to provide a stacking arrangement for the printedmultiples wherein the printed card of each level may be removed orreplaced without requiring the disassembly of any other level in thestack.

One of the features of the invention is the manner of preparing thecards for a series of selector banks whereby a printed multiple isprovided for the corresponding contacts of adjacent banks and themultiples of adjacent levels are shielded one from the other. Each levelincludes a card of dielectric material having conductors in the form ofnarrow strips on one side to constitute the horizontal multiple and alayer of conductive material extending over substantially the entirearea of the other side to constitute an electrostatic shield between thehorizontal multiple of its level and the horizontal multiple oi the nextadjacent level. The contacts for each bank are provided in an are alongone edge of the card preferably on both sides of the card withinterconnections extending through the card. The contacts on the sidecontaining. a layer of conductive material together with theleadstherefor are formed by narrow channels in the conductive layer. Theleads thus formed extend crosswise of the card and are connected throughthe card to the corresponding conductors of the horizontal multiples onthe opposite side. These cards together .with spacing cards ofdielectric material are assembled and aligned wtih clamping means. Toremove or replace any one card the aligning means are first removed andthe clam-ping means loosened thereby permitting such removal orreplacement.

Another of the features of the invention is the manner of preparing thecardsfor a series of line selector banks whereby a printed multiplee ofall conductors forming one side ofi the pairs of conductors within thelevel assembly are the mirror image of all the conductors forming theother side of the pairs of conductors within the level assembly, thusbringing the two conductors of each pair in 'very close proximitythroughout the entire length of the of, the card containing theconductive shield and leads to the contacts;

multiple conductors 2-12.

3,081,416 Patented Mar. 12, 1963 FIG. 2 shows in plan the opposite sideof the card illustrated in FIG. 1;

FIGS. 3 and 4 show in plan two cards which are combined to provide oneunit of the line bank;

FIG. 5 shows a bank stack assembly in longitudinal cross-section ofprinted cards and dielectric spacers, the section being taken along lineS -S of FIG. 1; and

FIG. 6 is a view in vertical cross-section of a bank stack taken alongline 6 6- of FIG. 1.

In the prior art telephone bank switches are interconnected byindividual wire leads which have substantial loops to permit changes inconnections, if errors have been made in the connections, as oftenhappens. The result is that such wired apparatus present a clumsy anduntidy appearance in addition to being susceptible to errors. It hasbeen proposed to use in telephone switchboard assemblies electricalconnecting strip made from metallic foil and folded over to provide asuccession of multiple connections which may be used in telephoneswitchboard assemblies. However this proposed method, while iteliminates wires, does not have continuous strip conductors but providesconnections from one switch group to another in a repetitive fashion.

Referring to FIGS. 1, 2 and 6 of the drawings, each level of the privatebank portion of the step-bystep switch is shown to comprise a dielectriccard 1 which has on one side thereof a plurality of conductors 2 to 12in the form of narrow strips extending lengthwise of the card whichcomprise the horizontal multiple connecting corresponding contacts of aplurality of banks, such as indicated by the two adjacent arcuatesections 13 and '14 in FIGS. 1

and 2. Each bank section includes eleven contacts which are printed onthe same side oi the card as the horizontal The contacts 15 of the endsection 13- are connected directly to the ends of the conductors 2-12but the contacts 16 of the other sections, such as at 14, are connectedto corresponding conductors of the horizontal multiple by leads formedin the conductive "shield 17 through contacts 16a on the other side ofthe card. These leads are indicated at 18.

While the printing of the conductive material on the dielectric card'mayfollow any one of many different circuit printing techniques, the onedescribed herein for purposes of illustration is commonly refer-red toas the etching method. The dielectric card 1 may be of any suitabledielectric, either polyethylene, polystyrene, Teflon, fiber glass orlaminations of fiber glass and Teflon. The cards are originally cladwith copper foil on each side'and the portions to be retained are coatedwith acid resisting material after which the card is subjected to anacid etching solution which removes the unwanted portions of the copperfoil. The side 015 the card shown in FIG. 1 comprises the shield inwhich the contact areas ductors of the horizontal multiple on theopposite side.

Each opening 22 is shown to be connected through the card to acorresponding horizontal conductor. The interconnection is usuallyformed by dipping the entire card in a bathof solder thereby forming allinterconnections simultaneously. The card 1 is also provided with narrowslots '23 between adjacent contact areas so as to avoid wiping particlesof dielectric onto the contacts. The corresponding contact areas 15, 15aand 16, 16a on cpposite sides of the card are interconnected by openings24 which are soldered during the solder-dipping operation.

The leads 18 are similarly connected to corresponding conductors of thehorizontal multiple as indicated by the interconnection 24.

From the foregoing description it will be clear that the card for theprivate bank comprises a dielectric member on which the conductors ofthe horizontal multiple are printed on one side together withcorresponding contacts for each section. The other side of the card iscovered with a layer of conductive material 17 in which contact areasand leads are formed by narrow Channels formed in the conductivematerial 17. This leaves that side of the card substantially coveredwith conductive material which when the card is assembled with othercards in a stack, the layer 17 constitutes an electrostatic shieldbteween the horizontal multiples of adjacent levels. This formation isclearly illustrated in FIG. 6 wherein cards 26 and 27 comprise adjacentlevels separated by a layer of dielectric 28. The layer of conductivematerial 17 of the card 27 comprises the shield between the horizontalmultiple of the card 27 and the horizontal multiple of the next adjacentcard 26.

FIGS. 3 and 4 show the construction of the cards of the line bank. Theyare formed similarly as described for the cards of the private bank. Inthe illustrations of FIGS. 3 and 4, the printing on the opposite sidesin each view is shown in dotted lines. Each level of the line bank,however, comprises two such cards, FIG. 3 showing card 29 and FIG. 4showing card 30', the two being separated by a thin layer of dielectricas shown in cross section of FIG. 6. FIG. 3 shows the card 29 as viewedfrom the top in FIG. 6, while the card 30 shown in FIG. 4 is viewed fromthe bottom of FIG. 6.

Referring particularly to FIG. 3 the card 29 is shown to have contactareas 32 which are separated by dummy contacts 33. The space betweeneach dummy contact and the adjacent active contact may include a slot 34which extends through the card. Each of the active contacts 32 areconnected by leads 35 formed on the opposite side of the card forconnection with corresponding conductors 36 of the horizontal multiple.The end section of the card is also provided with terminals 37 which arelikewise provided with leads 38 formed in the electrostatic shield forconnection through the card to corresponding conductors of thehorizontal multiple.

Referring to FIG. 4 the card is formed in a similar manner except thatthe printing is directly opposite to that shown in FIG. 3 whereby thetwo cards may be assembled with the horizontal multiples directlyopposed as shown in FIG. 6. The active contacts for card 30 areindicated at 39 and the horizontal multiples are indicated at 40. Theconductive shields for the cards 29 and 30 are indicated at 41 and 42.In manufacture these cards 29 and 30 are assembled with a thinintervening layer of dielectric 31 and sealed together to form a singleunit. In assembling cards 29 and 30 it is important to space themtogether as close as possible. This is accomplished by making thethickness of the sheet of dielectric 31 in the neighborhood of .005inch. This brings the conductor strips into mirror image relationshipthroughout the lengths of the cards, and the conductive layers 41 and42. form in effect a shield between the conductor pairs of the level,each conductor pair being the two corresponding strips, such as 54 and55 (FIGS. 3, 4 and 6) of cards 29 and 30 on opposite sides of thedielectric 31.

These units are assembled together with dielectric spacing layers 43 toform the assembled bank. The cards of the bankas indicated in FIG. arealigned by threaded rods 44 and 45 which pass through alignment openings46, FIG. 1, and 47, FIG. 3. The cards are clamped between two framemembers 48 and 49 by end bolts 50. The elements 44 and 45 are threadablyreceived in the frame member 49. When it is desirable to remove orreplace one of the cards or assembled units 29-30, the alignment rods 44and 45 are removed and the clamping bolts 50 loosened. This permits theremoval of any desired card without disassembling the other cards.

In FIG. 6 the wipers are inlicated in dotted lines. For the private banka double contact wiper is shown at 51 which engages the correspondingcontact areas of the card as the wiper is moved along the arc containingthe contacts. The wipers '52 and 53 comprise the wipers for the linebank, the wiper 52 engaging the active contacts of card 29 while thewiper 53 engages active contacts of card 30.

While we have described above the principles of our invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of our invention as set forth in the objects thereof and inthe accompanying claims.

We claim:

1. A switch contact bank assembly comprising a plurality of levels eachprovided with a plurality of conductors coupled as the horizontalmultiple to successive groups of contacts, each of said levelscomprising a card of dielectric material having continuous conductivestrips extending lengthwise of said card constituting the horizontalmultiple and a plurality of first groups of contacts on one side, and aseparate layer of conductive material in a given plane on the other,extending over substantially the entire area thereof to constitute, ineffect, an electrostatic shield relative to said conductive strips, saidlayer of conductive material having narrow channels therein to defineconductive leads between adjacent channels separated by portions of saidconductive material, said separating conductive material constituting,in effect, an electrostatic shield between said leads, meansconductively connecting said conductive leads through said card tocorresponding ones of said conductive strips, a plurality of a secondgroup of contacts on said other side opposite said plurality of firstgroups of contacts, each one of a second group of contacts beingconnected to a corresponding one of said oppositely disposed first groupof contacts through said card, and means connecting each coupled pair ofoppositely disposed contacts to a connected conductive lead andconductive strip, said first and second group of contacts being adaptedfor engagement by a contact wiper.

2. A switch contact bank assembly according to claim 1 wherein saidconductive leads extend substantially crosswise of said card, and saidfirst and second groups of contacts are disposed in arcuate portionsalong one edge of said card.

3. A switch contact bank assembly comprising a plurality of levels eachprovided with a plurality of conductors coupled as thehorizontalmultiple to successive groups of contacts, each of said card-scomprising a card of dielectric material having continuous conductivestrips on one side extending lengthwise of said card constituting saidhorizontal multiple and a plurality of first groups of contacts on saidside, and a separate layer of conductive material in a given plane onthe other side extending over substantially the entire area thereof toconstitute, in efiect, an electrostatic shield between the horizontalmultiple of its level and the horizontal multiple of the next adjacentlevel, said layer of conductive material having narrow channels thereinto define conductive leads between adjacent channels separated byportions of said conductive material, said separating conductivematerial constituting, in effect,

an electrostatic shield between said leads, means conductivelyconnecting said conductive leads through said card to corresponding onesof said conductive strips, a plurality of second groups of contacts onsaid other side opposite said plurality of first groups of contacts,each one of a second group of contacts being connected to acorresponding one of said oppositely disposed first group of contactsthrough said card and means connecting each coupled pair of oppositelydisposed contacts to a connected conductive lead and conductive strip,said contacts of said first and second groups being adapted forengagement by a contact wiper.

4. A switch contact bank assembly comprising a plurality of levels eachprovided with a plurality of conductors coupled as the horizontalmultiple to successive groups of contacts, at least certain of saidlevels compris ing two cards of dielectric material each said cardhaving conductive strips on one side constituting said horizontalmultiple and a first group of contacts on said side, and a separatelayer of conductive material ina given plane on the other, extendingover substantially the entire area thereof to constitute, in effect, anelectrostatic shield relative to said conductive strips, a layer ofdielectric material disposed between said cards with the sides carryingsaid horizontal multiple strips facing each other to form conductorpairs, the layer of conductive material of each of said cards havingnarrow channel-s therein to define conductive leads between adjacentchannels separated by portions of said conductive material, saidseparating conductive material constituting in effect an electrostaticshield between said leads, the conductive layers of said card-sconstituting, in effect, also an electrostatic shield between thehorizontal multiple of its level and the horizontal multiple of the nextadjacent level and between conductive pairs in the level, mean-s in eachcard conductively connecting said conductive leads through said card tocorresponding ones of said conducting strip, a second group of contactson said other side opposite said first group of contacts, each of saidsecond group of contacts being connected to a corresponding one of saidfirst group of contacts through said card, and means connecting eachcoupled pair of oppositely disposed contacts to a connected conductivelead and conductive strip, said contacts of said first and second groupbeing adapted for engagement by a contact wiper.

5. A switch contact bank assembly according to claim 4 furthercomprising a plurality of spacer cards of dielectric, means for aligningthe cards of said level with spacer cards therebetween and means zfiorclamping all of said cards together.

6. A switch contact bank assembly comprising a plurality of levels eachprovided with a plurality of conduc tors coupled as the horizontalmultiple to successive groups of cont-acts, each of said levelscomprising a pair of cards of dielectric material, each said cardshaving conductive strips constituting said horizontal multiple and afirst group of contacts on one side, a separate layer of conductivematerial in a given plane on the other side, extending oversubstantially the entire area thereof to constitute, in effect, anelectrostatic shield relative to said conductive strips, said layer ofconductive material having narrow channel-s therein to define conductiveleads between adjacent channels separated by portions of saidconconductive material, said separating conductive materialconstituting, in effect, an electrostatic shield between said leads,means conductively connecting said conductive leads through said card tocorresponding ones of said conductive strips, a second group of contactson said other side opposite said first group of contacts, each of saidsecond group of contacts being connected to a corresponding one of saidfirst group of contacts through said card, and means connecting eachcoupled pair of oppositely disposed contacts to a connected conductivelead and conductive strip, said contacts of said first and second groupsbeing adapted for engagement by a contact wiper, means disposing saidpair of cards in parallel dielectrlcally spaced relation with theconductive strips of each card facing each other as a mirror image ofthe corresponding conductive strips of the other card whereby theconductor pairs comprise one top conductor and one bottom conductordisposed parallel and in close proximity throughout their length, thusminimizing electrostatic and electromagnetic interaction between pairsof conductors in the levels.

7. A multiple conductor card comprising a card of dielectric materialhaving continuous conductive strips extending lengthwise of said cardand a plurality of first groups of contacts on one side, and a separatelayer of conductive material in a given plane on the other side,extending over substantially the entire area thereof to constitute, ineffect, an electrostatic shield relative to said conductive strips, saidlayer of conductive material having narrow channels therein definingconductive leads between adjacent channels separated by portions of saidconductive material, said separating conductive material constituting,in effect, an electrostatic shield between said leads, meansconductively connecting said conductive leads through said card tocorresponding ones of said conductive strips, a plurality of secondgroups of contacts on said other side opposite said plurality of firstgroups of contacts, eachone of a second group of contacts beingconnected to a corresponding one of said oppositely disposed first groupof contacts through said card, and means connecting each coupled pair ofoppositely disposed contacts to a connected conductive lead andconductive strip, said contacts of said first and second groups beingadapted for engagement by a contact wiper.

8. A multiple conductor card according to claim 7 wherein saidconductive leads extend substantially crosswise of said card, and saidfirst group and second group of contacts are disposed in arcuateportions along one edge of said card.

References Cited in the file of this patent UNITED STATES PATENTS552,058 German Apr. 30, 1924 1,819,675 Chaplin Aug. 18, 1931 2,257,894Winsor Oct. 7, 1941 2,259,103 Drake Oct. 14, 1941 2,298,236 SiegmundOct. 6, 1942 2,441,960 Eisler May 25, 1948 2,586,854 Myers Feb. 26, 19522,616,994 Luhn Nov. 4, 1952, 2,634,310 Eisler Apr. 7, 1953 2,695,963Thias Nov. 30, 1954

1. A SWITCH CONTACT BANK ASSEMBLY COMPRISING A PLURALITY OF LEVELS EACH PROVIDED WITH A PLURALITY OF CONDUCTORS COUPLED AS THE HORIZONTAL MULTIPLE TO SUCCESSIVE GROUPS OF CONTACTS, EACH OF SAID LEVELS COMPRISING A CARD OF DIELECTRIC MATERIAL HAVING CONTINUOUS CONDUCTIVE STRIPS EXTENDING LENGTHWISE OF SAID CARD CONSTITUTING THE HORIZONTAL MULTIPLE AND A PLURALITY OF FIRST GROUPS OF CONTACTS ON ONE SIDE, AND A SEPARATE LAYER OF CONDUCTIVE MATERIAL IN A GIVEN PLANE ON THE OTHER, EXTENDING OVER SUBSTANTIALLY THE ENTIRE AREA THEREOF TO CONSTITUTE, IN EFFECT, AN ELECTROSTATIC SHIELD RELATIVE TO SAID CONDUCTIVE STRIPS, SAID LAYER OF CONDUCTIVE MATERIAL HAVING NARROW CHANNELS THEREIN TO DEFINE CONDUCTIVE LEADS BETWEEN ADJACENT CHANNELS SEPARATED BY PORTIONS OF SAID CONDUCTIVE MATERIAL, SAID SEPARATING CONDUCTIVE MATERIAL CONSTITUTING, IN EFFECT, AN ELECTROSTATIC SHIELD BETWEEN SAID LEADS, MEANS CONDUCTIVELY CONNECTING SAID CONDUCTIVE LEADS THROUGH SAID CARD TO CORRESPONDING ONES OF SAID CONDUCTIVE STRIPS, A PLURALITY OF A SECOND GROUP OF CONTACTS ON SAID OTHER SIDE OPPOSITE SAID PLURALITY OF FIRST GROUPS OF CONTACTS, EACH ONE OF A SECOND GROUP OF CONTACTS BEING CONNECTED TO A CORRESPONDING ONE OF SAID OPPOSITELY DISPOSED FIRST GROUP OF CONTACTS THROUGH SAID CARD, AND MEANS CONNECTING EACH COUPLED PAIR OF OPPOSITELY DISPOSED CONTACTS TO A CONNECTED CONDUCTIVE LEAD AND CONDUCTIVE STRIP, SAID FIRST AND SECOND GROUP OF CONTACTS BEING ADAPTED FOR ENGAGEMENT BY A CONTACT WIPER. 